| Title | Geological Thermal Energy Storage for Long Duration Energy Storage Applications |
|---|---|
| Authors | Joshua McTigue |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | thermal energy storage; underground thermal energy storage; geological thermal energy storage; long duration energy storage; carnot battery; solar thermal |
| Abstract | Geological thermal energy storage (GeoTES) utilizes subsurface reservoirs to store thermal energy for power generation and direct-use heating and cooling. This approach significantly enhances the use of low-temperature reservoirs and may also utilize depleted oil and gas reservoirs. GeoTES may integrate with a variety of energy sources (such as concentrating solar power, waste heat, or surplus electricity from variable renewables) and deliver a range of energy services, such as energy capacity, security and resiliency, ancillary grid services, combined heat and power, and data center cooling. In this article, we will discuss the suitability of GeoTES for Long Duration Energy Storage (LDES) applications. Previous work has indicated that GeoTES has low marginal costs of energy storage capacity, making it particularly competitive for LDES. In this article, we describe updated techno-economic models developed by a consortium of national labs and industry experts to provide updated cost estimates for GeoTES. Furthermore, we investigate whether suitable geological formations exist and whether they can store enough energy to benefit the grid. A survey of geological formations in California and Texas was conducted with data collected from a range of sources. A high-level capacity estimation tool was developed to estimate the potential energy capacity of specific formations. We apply to tool to four reservoirs across California and Texas and suggest that suitable reservoirs could store > 100 TWh-th, equivalent to >10 TWh-e, if the thermal energy is converted to electricity. This suggests that GeoTES can scale to have a large impact on the electrical grid. |